Synthesis of the angiotensin-converting enzyme inhibitors (-)-A58365A and (-)-A58365B from a common intermediate

(-)-A58365A (1) and (-)-A58365B (2), which are inhibitors of angiotensin-converting enzyme, were synthesized from the subunits 9 and 10. These were coupled, and the resulting individual amides 17a,b were converted by ozonolysis into aldehydes 18a,b, which underwent cyclodehydration to the enamides 19a,b. Treatment with a stannane served to generate the vinyl stannanes 20a,b, from which ketones 22a,b were produced by protodestannylation and ozonolysis. Base treatment and hydrogenolysis then afforded (-)-A58365A (1). The intermediates 17a,b were also converted into aldehydes 26a,b by hydroboration and oxidation, and a similar sequence to that used for (-)-A58365A was then applied in order to complete the first enantiospecific synthesis of the congener, (-)-A58365B (2).